Lenovo 300S-14isk notebook battery and adapter cannot be serviced at the same time

Lenovo 300S-14isk notebook battery and adapter cannot be serviced at the same time.

Check the main power supply of 24780. According to Manual 24780, the output of 24-pin REGN 6-V linear regulator is provided by VCC. The LDO is active when ACDET is higher than 0.6V and VCC is higher than UVLO. After changing PR4413 to 10 ohms, the fault was eliminated and all problems were solved.

Machine model: Lenovo 300S-14isk notebook

Board number: 14292-1

Symptoms: The battery and adapter cannot be used at the same time.

Maintenance process:

A Lenovo 300S-14isk notebook, the battery and the adapter can’t be used at the same time. The adapter works normally, but it can’t get into the system as long as the battery is plugged in, or the power indicator is flashing. You can use the battery alone.

Lenovo 300S-14isk notebook battery and adapter can’t be serviced at the same time Figure 1

At the same time, plug, short circuit, either the adapter side isolation tube short circuit, or battery isolation tube short circuit. Disassembly and measurement of all pipes are normal.

Lenovo 300S-14isk notebook battery and adapter can’t be serviced at the same time Figure 2

When the battery is plugged in, it can be adjusted, and the machine cannot be charged. First, change the charging chip, and the fault becomes that the adapter loses power when it is turned on. When it is powered up to 0.5, it is all the same whether the memory is plugged in or not. When the original charging chip is replaced, the fault remains the same, but the power is lost, and the display is not displayed. The BIOS is still the same. But when the battery is turned on, it can be displayed.

Lenovo 300S-14isk notebook battery and adapter can’t be serviced at the same time Figure 3

Measure the working condition of the charging chip, 24780. The first signal ACOK 0V, disconnecting the node, is also 0V. The problem is on the charging chip side.

Lenovo 300S-14isk notebook battery and adapter can’t be serviced at the same time Figure 4

Lenovo 300S-14isk notebook battery and adapter can’t be serviced at the same time Figure 5

Tracing ACIN requires a reference voltage division of 24780. After measuring and disconnecting the charging chip ACOK, it only needs 0.6V here, but it actually needs 3.3V

Lenovo 300S-14isk notebook battery and adapter can’t be serviced at the same time Figure 6

Tracing PWR_CHG_REGN reference voltage is only 1.18V, which is normally 6V.

Lenovo 300S-14isk notebook battery and adapter can’t be serviced at the same time Figure 7

Connect a ceramic capacitor ≥2.2μF 0603 from REGN to GND, and the diode between REGN and BTST is integrated!

Actually, the measured 6-pin ACDET 2.67V is normal, the main power supply is 28 pins, only 2.49V, and the measured resistance of 28 pins is close to infinity.